diff --git a/include/libimp/error.h b/include/libimp/error.h
index 741b36a..ab0c60a 100644
--- a/include/libimp/error.h
+++ b/include/libimp/error.h
@@ -7,14 +7,16 @@
 #pragma once
 
 #include <string>
+#include <cstdint>
 
 #include "libimp/def.h"
 #include "libimp/export.h"
-#include "libimp/result.h"
 #include "libimp/fmt_cpo.h"
 
 LIBIMP_NAMESPACE_BEG_
 
+using error_code_t = std::uint64_t;
+
 /**
  * \brief Serves as the base class for specific error category types.
  * \see https://en.cppreference.com/w/cpp/error/error_category
@@ -29,7 +31,7 @@ public:
 
   /// \brief observer
   virtual std::string name() const = 0;
-  virtual std::string message(result_code r) const = 0;
+  virtual std::string message(error_code_t const &r) const = 0;
 
   /// \brief comparison function
   bool operator==(error_category const &rhs) const noexcept;
@@ -46,17 +48,16 @@ LIBIMP_EXPORT error_category const &generic_category() noexcept;
  * \see https://en.cppreference.com/w/cpp/error/error_code
  */
 class LIBIMP_EXPORT error_code {
-  result_code r_code_;
+  error_code_t e_code_;
   error_category const *ec_;
 
 public:
   /// \brief constructors
   error_code() noexcept;
-  error_code(result_code r, error_category const &ec) noexcept;
+  error_code(error_code_t const &r, error_category const &ec) noexcept;
 
   /// \brief observers
-  result_code code() const noexcept;
-  result_type value() const noexcept;
+  error_code_t code() const noexcept;
   error_category const &category() const noexcept;
   std::string message() const;
   explicit operator bool() const noexcept;
diff --git a/include/libimp/result.h b/include/libimp/result.h
index 9c5f813..f7b37ca 100644
--- a/include/libimp/result.h
+++ b/include/libimp/result.h
@@ -19,25 +19,26 @@
 
 LIBIMP_NAMESPACE_BEG_
 
-using result_type = std::tuple<std::uint64_t, bool>;
+using result_code_t = std::uint64_t;
+using result_type   = std::tuple<result_code_t, bool>;
 
 /**
- * \brief Use the least significant (in Little-Endian) of 
- * a 64-bit unsigned integer to indicate success or failure,
- * so the data significant bit cannot exceed 63 bits.
+ * \class class LIBIMP_EXPORT result_code
+ * \brief Uses std::uint64_t as the default underlying type of error code.
  */
 class LIBIMP_EXPORT result_code {
   result_type status_;
 
 public:
   result_code() noexcept;
-  result_code(result_type value) noexcept;
-  result_code(bool ok, result_type value) noexcept;
+  result_code(result_code_t value) noexcept;
+  result_code(result_type const &value) noexcept;
+  result_code(bool ok, result_code_t value) noexcept;
 
-  result_type value() const noexcept;
+  result_code_t value() const noexcept;
   bool ok() const noexcept;
 
-  result_type operator*() const noexcept {
+  result_code_t operator*() const noexcept {
     return value();
   }
   explicit operator bool() const noexcept {
@@ -68,7 +69,7 @@ struct default_traits<T, std::enable_if_t<std::is_integral<T>::value>> {
     code = {};
   }
   constexpr static void init_code(result_code &code, bool ok, T value) noexcept {
-    code = {ok, static_cast<result_type>(value)};
+    code = {ok, static_cast<result_code_t>(value)};
   }
   constexpr static void init_code(result_code &code, T value) noexcept {
     init_code(code, true, value);
@@ -94,12 +95,12 @@ template <typename T>
 struct default_traits<T, std::enable_if_t<std::is_pointer<T>::value>> {
   /// \brief Custom initialization.
   constexpr static void init_code(result_code &code, T value = default_value()) noexcept {
-    code = {default_value() != value, reinterpret_cast<result_type>(value)};
+    code = {default_value() != value, reinterpret_cast<result_code_t>(value)};
   }
   constexpr static void init_code(result_code &code, std::nullptr_t) noexcept {
     code = {false, {}};
   }
-  constexpr static void init_code(result_code &code, std::nullptr_t, result_type r) noexcept {
+  constexpr static void init_code(result_code &code, std::nullptr_t, result_code_t r) noexcept {
     code = {false, r};
   }
 
@@ -124,6 +125,10 @@ struct default_traits<T, std::enable_if_t<std::is_pointer<T>::value>> {
 
 } // namespace detail_result
 
+/**
+ * \class class result
+ * \brief The generic wrapper for the result_code.
+ */
 template <typename T, typename TypeTraits>
 class result : public TypeTraits {
 
@@ -144,7 +149,7 @@ public:
   bool ok() const noexcept { return code_.ok(); }
   T value() const noexcept { return type_traits_t::cast_from_code(code_); }
 
-  result_type code_value() const noexcept { return code_.value(); }
+  result_code_t code_value() const noexcept { return code_.value(); }
 
   T operator*() const noexcept {
     return value();
diff --git a/include/libimp/system.h b/include/libimp/system.h
index f5967bb..aed8d7c 100644
--- a/include/libimp/system.h
+++ b/include/libimp/system.h
@@ -13,6 +13,7 @@
 #include "libimp/def.h"
 #include "libimp/export.h"
 #include "libimp/error.h"
+#include "libimp/result.h"
 
 LIBIMP_NAMESPACE_BEG_
 namespace sys {
@@ -20,13 +21,13 @@ namespace sys {
 /**
  * \brief Get/Set the system error number
  */
-LIBIMP_EXPORT result_code error_no() noexcept;
-LIBIMP_EXPORT void error_no(result_code) noexcept;
+LIBIMP_EXPORT error_code_t error_no() noexcept;
+LIBIMP_EXPORT void error_no(error_code_t const &) noexcept;
 
 /**
  * \brief Gets a text description of the system error
  */
-LIBIMP_EXPORT std::string error_str(result_code) noexcept;
+LIBIMP_EXPORT std::string error_str(error_code_t const &) noexcept;
 
 /**
  * \brief Identifies the operating system error category.
diff --git a/src/libimp/error.cpp b/src/libimp/error.cpp
index 7c4cafd..12de0f4 100644
--- a/src/libimp/error.cpp
+++ b/src/libimp/error.cpp
@@ -16,8 +16,8 @@ public:
   std::string name() const {
     return "generic";
   }
-  std::string message(result_code r) const {
-    return fmt(r.value(), (!r ? ", \"success\"" : ", \"failure\""));
+  std::string message(error_code_t const &r) const {
+    return fmt(r, ((r == 0) ? ", \"success\"" : ", \"failure\""));
   }
 };
 
@@ -29,17 +29,13 @@ error_category const &generic_category() noexcept {
 }
 
 error_code::error_code() noexcept
-  : r_code_{}, ec_{&generic_category()} {}
+  : error_code{0, generic_category()} {}
 
-error_code::error_code(result_code r, error_category const &ec) noexcept
-  : r_code_{r}, ec_{&ec} {}
+error_code::error_code(error_code_t const &r, error_category const &ec) noexcept
+  : e_code_{r}, ec_{&ec} {}
 
-result_code error_code::code() const noexcept {
-  return r_code_;
-}
-
-result_type error_code::value() const noexcept {
-  return r_code_.value();
+error_code_t error_code::code() const noexcept {
+  return e_code_;
 }
 
 error_category const &error_code::category() const noexcept {
@@ -47,15 +43,15 @@ error_category const &error_code::category() const noexcept {
 }
 
 std::string error_code::message() const {
-  return fmt("[", ec_->name(), ": ", ec_->message(r_code_), "]");
+  return fmt("[", ec_->name(), ": ", ec_->message(e_code_), "]");
 }
 
 error_code::operator bool() const noexcept {
-  return !!r_code_;
+  return e_code_ != 0;
 }
 
 bool operator==(error_code const &lhs, error_code const &rhs) noexcept {
-  return (lhs.r_code_ == rhs.r_code_) && (*lhs.ec_ == *rhs.ec_);
+  return (lhs.e_code_ == rhs.e_code_) && (*lhs.ec_ == *rhs.ec_);
 }
 
 bool operator!=(error_code const &lhs, error_code const &rhs) noexcept {
diff --git a/src/libimp/platform/posix/system.h b/src/libimp/platform/posix/system.h
index c8dc591..483d119 100644
--- a/src/libimp/platform/posix/system.h
+++ b/src/libimp/platform/posix/system.h
@@ -32,7 +32,7 @@ result_code error_no() noexcept {
  * \brief Set the system error number
  * https://man7.org/linux/man-pages/man3/errno.3.html
  */
-void error_no(result_code code) noexcept {
+void error_no(result_code const &code) noexcept {
   errno = code ? ENOERR : (int)code.value();
 }
 
@@ -41,7 +41,7 @@ void error_no(result_code code) noexcept {
  * https://man7.org/linux/man-pages/man3/strerror_l.3.html
  * https://manpages.ubuntu.com/manpages/xenial/en/man3/strerror.3.html
  */
-std::string error_str(result_code code) noexcept {
+std::string error_str(result_code const &code) noexcept {
   char msg_buf[256] {};
 #if ((_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600) && !_GNU_SOURCE)
   LIBIMP_LOG_();
diff --git a/src/libimp/platform/win/system.h b/src/libimp/platform/win/system.h
index 4a831ad..9cfe4ab 100644
--- a/src/libimp/platform/win/system.h
+++ b/src/libimp/platform/win/system.h
@@ -24,20 +24,20 @@ namespace sys {
  * \brief Get the system error number
  * https://docs.microsoft.com/en-us/windows/win32/api/errhandlingapi/nf-errhandlingapi-getlasterror
  */
-result_code error_no() noexcept {
+error_code_t error_no() noexcept {
   auto err = ::GetLastError();
   if (err == ERROR_SUCCESS) {
     return {ERROR_SUCCESS};
   }
-  return {false, std::uint64_t(err)};
+  return error_code_t(err);
 }
 
 /**
  * \brief Set the system error number
  * https://docs.microsoft.com/en-us/windows/win32/api/errhandlingapi/nf-errhandlingapi-setlasterror
  */
-void error_no(result_code code) noexcept {
-  DWORD err = code ? ERROR_SUCCESS : (DWORD)code.value();
+void error_no(error_code_t const &code) noexcept {
+  DWORD err = (code == 0) ? ERROR_SUCCESS : (DWORD)code;
   ::SetLastError(err);
 }
 
@@ -45,10 +45,10 @@ void error_no(result_code code) noexcept {
  * \brief Gets a text description of the system error
  * https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-formatmessage
  */
-std::string error_str(result_code code) noexcept {
+std::string error_str(error_code_t const &code) noexcept {
   LIBIMP_LOG_();
   LIBIMP_TRY {
-    DWORD err = (DWORD)code.value();
+    DWORD err = (DWORD)code;
     LPTSTR lpErrText = NULL;
     if (::FormatMessage(
           FORMAT_MESSAGE_ALLOCATE_BUFFER | 
diff --git a/src/libimp/result.cpp b/src/libimp/result.cpp
index 4036fe8..55a9941 100644
--- a/src/libimp/result.cpp
+++ b/src/libimp/result.cpp
@@ -3,38 +3,26 @@
 #include "libimp/horrible_cast.h"
 
 LIBIMP_NAMESPACE_BEG_
-namespace {
-
-struct result_code_info {
-  std::uint64_t ok  : 1;
-  std::uint64_t code: 63;
-};
-
-std::uint64_t make_status(bool ok, std::uint64_t code) noexcept {
-  return horrible_cast<std::uint64_t>(result_code_info{(ok ? 1ull : 0ull), code});
-}
-
-result_code_info info_cast(std::uint64_t status) noexcept {
-  return horrible_cast<result_code_info>(status);
-}
-
-} // namespace
 
 result_code::result_code() noexcept
   : result_code(false, {}) {}
 
-result_code::result_code(std::uint64_t value) noexcept
+result_code::result_code(result_code_t value) noexcept
   : result_code(true, value) {}
 
-result_code::result_code(bool ok, std::uint64_t code) noexcept
-  : status_(make_status(ok, code)) {}
+result_code::result_code(result_type const &value) noexcept
+  : result_code(std::get<bool>(value), 
+                std::get<result_code_t>(value)) {}
 
-std::uint64_t result_code::value() const noexcept {
-  return info_cast(status_).code;
+result_code::result_code(bool ok, std::uint64_t code) noexcept
+  : status_(code, ok) {}
+
+result_code_t result_code::value() const noexcept {
+  return std::get<result_code_t>(status_);
 }
 
 bool result_code::ok() const noexcept {
-  return info_cast(status_).ok != 0;
+  return std::get<bool>(status_);
 }
 
 bool operator==(result_code const &lhs, result_code const &rhs) noexcept {
diff --git a/src/libimp/system.cpp b/src/libimp/system.cpp
index d71167b..2ec307a 100644
--- a/src/libimp/system.cpp
+++ b/src/libimp/system.cpp
@@ -15,8 +15,8 @@ public:
   std::string name() const {
     return "system";
   }
-  std::string message(::LIBIMP::result_code r) const {
-    return ::LIBIMP::fmt(r.value(), ::LIBIMP::sys::error_str(r));
+  std::string message(::LIBIMP::error_code_t const &r) const {
+    return ::LIBIMP::fmt(r, ::LIBIMP::sys::error_str(r));
   }
 };
 
diff --git a/src/libipc/platform/win/mmap_impl.h b/src/libipc/platform/win/mmap_impl.h
index e77e06c..6466b41 100644
--- a/src/libipc/platform/win/mmap_impl.h
+++ b/src/libipc/platform/win/mmap_impl.h
@@ -78,7 +78,7 @@ result<HANDLE> mmap_open(std::string const &file, std::size_t size, mode::type t
     if (h == NULL) {
       auto err = sys::error();
       log.error("failed: OpenFileMapping(FILE_MAP_ALL_ACCESS, FALSE, ", file, "). error = ", err);
-      return {nullptr, err.value()};
+      return {nullptr, err.code()};
     }
     return h;
   };
@@ -91,7 +91,7 @@ result<HANDLE> mmap_open(std::string const &file, std::size_t size, mode::type t
     if (h == NULL) {
       auto err = sys::error();
       log.error("failed: CreateFileMapping(PAGE_READWRITE | SEC_COMMIT, ", size, ", ", file, "). error = ", err);
-      return {nullptr, err.value()};
+      return {nullptr, err.code()};
     }
     return h;
   };
@@ -133,7 +133,7 @@ result<LPVOID> mmap_memof(HANDLE h) {
   if (mem == NULL) {
     auto err = sys::error();
     log.error("failed: MapViewOfFile(", h, ", FILE_MAP_ALL_ACCESS). error = ", err);
-    return {nullptr, err.value()};
+    return {nullptr, err.code()};
   }
   return mem;
 }
@@ -152,7 +152,7 @@ result<SIZE_T> mmap_sizeof(LPCVOID mem) {
   if (::VirtualQuery(mem, &mem_info, sizeof(mem_info)) == 0) {
     auto err = sys::error();
     log.error("failed: VirtualQuery(", mem, "). error = ", err);
-    return {false, (SIZE_T)err.value()};
+    return {false, (SIZE_T)err.code()};
   }
   return mem_info.RegionSize;
 }
diff --git a/src/libipc/platform/win/shm_impl.h b/src/libipc/platform/win/shm_impl.h
index 5291fe5..9ff5dea 100644
--- a/src/libipc/platform/win/shm_impl.h
+++ b/src/libipc/platform/win/shm_impl.h
@@ -34,7 +34,7 @@ result<shm_t> shm_open(std::string name, std::size_t size, mode::type type) noex
   if (!sz) {
     log.error("failed: mmap_sizeof(", *mem, ").");
     mmap_close(*h);
-    return {nullptr, static_cast<result_type>(sz.value())};
+    return {nullptr, static_cast<result_code_t>(sz.value())};
   }
   return new shm_handle{std::move(name), *sz, *mem, *h};
 }
diff --git a/test/imp/test_imp_error.cpp b/test/imp/test_imp_error.cpp
index d985a3b..9534743 100644
--- a/test/imp/test_imp_error.cpp
+++ b/test/imp/test_imp_error.cpp
@@ -13,8 +13,8 @@ public:
   std::string name() const {
     return "custom";
   }
-  std::string message(imp::result_code r) const {
-    return !r ? "success" : "failure";
+  std::string message(imp::error_code_t const &r) const {
+    return (r == 0) ? "success" : "failure";
   }
 };
 
diff --git a/test/imp/test_imp_result.cpp b/test/imp/test_imp_result.cpp
index c6b6177..757038e 100644
--- a/test/imp/test_imp_result.cpp
+++ b/test/imp/test_imp_result.cpp
@@ -90,4 +90,8 @@ TEST(result, fmt) {
     imp::result<int *> r5;
     EXPECT_EQ(imp::fmt(r5), "[fail, value = null, code = 0]");
   }
+  {
+    imp::result<std::int64_t> r1 {-123};
+    EXPECT_EQ(imp::fmt(r1), imp::fmt("[succ, value = ", -123, "]"));
+  }
 }
\ No newline at end of file
diff --git a/test/imp/test_imp_system.cpp b/test/imp/test_imp_system.cpp
index d543596..e49f1f9 100644
--- a/test/imp/test_imp_system.cpp
+++ b/test/imp/test_imp_system.cpp
@@ -15,13 +15,13 @@
 #endif
 
 TEST(system, error_no) {
-  imp::sys::error_no({false, 111});
+  imp::sys::error_no(111);
   auto err = imp::sys::error_no();
-  EXPECT_FALSE(err);
-  EXPECT_EQ(err.value(), 111);
+  EXPECT_FALSE(err == 0);
+  EXPECT_EQ(err, 111);
 
   imp::sys::error_no({});
-  EXPECT_TRUE(imp::sys::error_no());
+  EXPECT_TRUE(imp::sys::error_no() == 0);
 
   auto e_msg = imp::sys::error_str(imp::sys::error_no());
   std::cout << e_msg << "\n";
@@ -51,7 +51,7 @@ TEST(system, error_str) {
   {
     std::string s_txt;
     imp::cvt_sstr(u16_err, s_txt);
-    EXPECT_EQ(imp::sys::error_str({false, ERROR_INVALID_HANDLE}), s_txt);
+    EXPECT_EQ(imp::sys::error_str(ERROR_INVALID_HANDLE), s_txt);
   }
 #else
   EXPECT_EQ(imp::sys::error_str({false, 1234}), "Unknown error 1234");